5x - 4y + 3 = 15 --- (1)
9y = 4x + 31 --- (2)
From (1), we have:
5x - 4y = 15 - 3
5x - 4y = 12
4y = 5x - 12
y = (5/4)x - 3 --- (3)
Substituting (3) into (2), we have:
9((5/4)x - 3) = 4x + 31
(45/4)x - 27 = 4x + 31
45x - 108 = 16x + 124
45x - 16x = 108 + 124
29x = 232
x = 232 / 29
x = 8
Substituting x = 8 into (3), we have:
y = (5/4)(8) - 3
y = 10 - 3
y = 7
Hence, the solution is (8, 7).